1. Field of the Invention
The present invention relates to a disk driving device for rotatively driving a disk-shaped information recording medium, such as a magnetic disk or an optical disk, to record or to reproduce information and, more particularly, to a disk driving device suitable for a so-called still video floppy disk and capable of intermittently moving a magnetic head radially of a magnetic disk rotating at a high rotating speed, and recording still video signals on or reproducing still video signals recorded on a track corresponding to a position where the magnetic head is located stationarily.
2. Description of the Prior Art
An exemplary disk driving device for recording and/or reproducing still video signals is disclosed in Japanese Patent Provisional Publication No. 58-57667. This known disk driving device has a cassette holder pivotally joined at one end thereof for swing motion to a base plate provided with a turntable. After receiving a magnetic sheet jacket (hereinafter referred to as "disk cartridge") therein, the cassette holder is turned toward the base plate to load the disk cartridge on the turntable. In the disk driving device of this kind, the cassette holder is formed integrally with a cover member, and the cover member is closed to move the disk cartridge downward to load the disk cartridge on the turntable. Accordingly, this disk driving device is designated as a top-loading type of disk driving device.
In addition to the top-loading type of disk driving device, a front-loading type of disk driving device is known. Generally the front-loading type of disk driving device comprises a holder which moves between a loading position and an ejecting position, a sliding plate which is always biased toward the disk cartridge inserting side, and raises or lowers the holder relative to the turntable during horizontal movement, and cam means formed in frame members along which the sliding plate slides. The cam means converts the movement of the disk cartridge parallel to the upper surface of the turntable into vertical movement of the same for disk cartridge loading and ejecting operations.
The top-loading type of disk driving device is simple in construction, because the cover member is pressed directly by the operator for loading the disk cartridge, which is advantageous in respect of the simplicity of the mechanism. However, the top-loading type of disk driving device has problems that the necessity of a space for opening the cover member restricts its intergrations with other equipment, that the disk cartridge loading operation is troublesome because the disk cartridge loading operation requires two kinds of actions, namely, inserting a disk cartridge into the holder, and then pressing the cover member toward the turntable, and that the position of the disk driving device is restricted in incorporating the disk driving device into other equipment and hence the design of the disk driving device is accompanied with many restrictions because the disk driving devices requires a space for opening the cover member.
On the other hand, in the front-loading type of disk driving device, the loading of a disk cartridge on the turntable can be achieved simply by inserting the disk cartridge into the holder. Accordingly, the front-loading type of disk driving device has advantages that the casing needs only a disk cartridge inserting opening not requiring any additional space for opening a cover member and that there is no restriction on the place of installation. The sliding plate of the front-loading type of disk driving device slides along a frame holding the components of the disk driving device including the turntable, the turntable driving mechanism, positioning pins and the carriage shifting mechanism. Therefore, the parts disposed in the vicinity of a predetermined path of the disk cartridge extending between the loading position and the ejecting position need to be formed so that the movement of the disk cartridge along the path is not obstructed and the sliding plate needs to be formed as thin as possible, and hence, in some cases, it is impossible to provide the sliding plate with a sufficient strength, which is a problem particularly in designing the disk driving device in a compact construction. Furthermore, the motor for driving the turntable is projected from the frame on the side opposite the side where the turntable is disposed so that the motor will not obstruct the movement of the sliding plate, which restricts the reduction of the disk driving device in thickness.